Arteries have thick, muscular walls that allow for constriction and flow direction, while veins have thin walls to carry blood.

Capillaries have extremely thin walls to allow exchange of oxygen, carbon dioxide, and nutrients with tissues, resulting in both oxygenated and deoxygenated blood in these vessels. Pressure in the arteries is always higher than in veins so that blood can be continuously pushed forward, negating the need for valves to prevent backflow. Such valves are present in veins and help to counteract gravity when returning blood to the heart.

Arteries have thick, muscular walls that allow for constriction and flow direction, while veins have thin walls to carry blood.

Capillaries have extremely thin walls to allow exchange of oxygen, carbon dioxide, and nutrients with tissues, resulting in both oxygenated and deoxygenated blood in these vessels. Pressure in the arteries is always higher than in veins so that blood can be continuously pushed forward, negating the need for valves to prevent backflow. Such valves are present in veins and help to counteract gravity when returning blood to the heart.

Gametocytes are eukaryotic germ line cells. They can undergo mitosis to form more gametocytes or undergo meiosis to form gametids. Male gametocytes are called spermatocytes and female gametocytes are called oocytes.

Toll-like receptors (TLRs) are a family of receptors found within innate immune antigen-presenting cells such as dendritic cells, monocytes, and macrophages. These receptors recognize specific elements of various infectious agents such as lipopolysaccharides, DNA, and RNA. Binding and activation of these receptors stimulates inflammatory responses and CD4/CD8 T-cell responses to drive an effective immune response.

TLRs do not control B-cell clonal selection, the process by which B-cells replicate to amplify the production of a certain antibody.

There are two major criteria that can be used to define nervous system categorizations. The first is location in the body. The central nervous system consists only of the brain and spinal cord, while the peripheral nervous system extends throughout the rest of the body. The central nervous system is enclosed by the blood-brain barrier, separating it from the rest of the body. The second classifier is mechanism of control. Some nervous pathways can be controlled voluntarily (somatic), while others are involuntary (autonomic).

The sympathetic and parasympathetic divisions are both peripheral autonomic pathways.

When the body temperature is too high, peripheral vasodilation can help exchange heat from the body to the environment. Warm blood from the center of the body is pumped to the extremities, which have a high surface area. The surface area is used to allow the heat from the blood to dissipate before it returns to the center of the body.

Peripheral vasoconstriction and shivering help increase the body temperature. Hyperventilation have no noticeable effect on body temperature.

The nervous system has two principle divisions for function and two principle divisions for structure. Structurally, there are the central and peripheral nervous system divisions. Functionally, there are the somatic and autonomic divisions.

The somatic nervous system is responsible for voluntary actions, namely the innervation of skeletal muscle. The autonomic nervous system is responsible for all involuntary actions, including smooth muscle contraction, glandular stimulation, and other functions.

The peripheral nervous system carries both somatic and autonomic signals, innervating the entire periphery (not just skeletal muscle). The sympathetic and parasympathetic divisions of the nervous system are both autonomic. Though they innervate some skeletal muscles, they also play keys roles in other bodily functions, such as heart rate and blood pressure regulation.

The somatic nervous system is the only division to only innervate skeletal muscle.

When the body temperature is too high, peripheral vasodilation can help exchange heat from the body to the environment. Warm blood from the center of the body is pumped to the extremities, which have a high surface area. The surface area is used to allow the heat from the blood to dissipate before it returns to the center of the body.

Peripheral vasoconstriction and shivering help increase the body temperature. Hyperventilation have no noticeable effect on body temperature.

Arteries have thick, muscular walls that allow for constriction and flow direction, while veins have thin walls to carry blood.

Capillaries have extremely thin walls to allow exchange of oxygen, carbon dioxide, and nutrients with tissues, resulting in both oxygenated and deoxygenated blood in these vessels. Pressure in the arteries is always higher than in veins so that blood can be continuously pushed forward, negating the need for valves to prevent backflow. Such valves are present in veins and help to counteract gravity when returning blood to the heart.

When the body temperature is too high, peripheral vasodilation can help exchange heat from the body to the environment. Warm blood from the center of the body is pumped to the extremities, which have a high surface area. The surface area is used to allow the heat from the blood to dissipate before it returns to the center of the body.

Peripheral vasoconstriction and shivering help increase the body temperature. Hyperventilation have no noticeable effect on body temperature.